I know this is an older thread, but I just want to update...
I was able to get a picture of the cat taken by a friend of mine on her phone and show it to the vet tech. Considering that the cat's scars and sores were mostly on her rump, I was given the all clear to administer the revolution treatment!

I am currently in the process of 'taming' the cat enough for her to let me put the treatment on her.
I really want this to work and not end up with an open and wasted tube of the precious medecine.